There is a problem with existing optical transceiver modules. When an un-cooled optical transceiver module is driven at low temperature, the ambient temperature influences a laser diode (LD) chip, and thus the wavelength of light generated in the LD chip is shifted. That is, when the ambient temperature is lowered during communication using a coarse wavelength division multiplexing (CWDM) scheme, there is a problem in that communication is not possible.
An auxiliary heater is used to maintain properties of the LD chip even at a lower temperature in an existing structure. In this case, the auxiliary heater is positioned between a radio frequency (RF) transmission line and a printed circuit board (PCB) connection portion. There is a problem in that the position of the auxiliary heater limits the length of the RF transmission line when the optical transceiver module is driven at a high frequency.